ZURICH, SWITZERLAND: IBM researchers in collaboration with scientists from the ETH Zurich have demonstrated a new, efficient and precise technique to print at the nanoscale. The method could advance the development of nanoscale biosensors, of lenses that can bend light inside future optical chips, and the fabrication of nanowires that might be the basis of tomorrow's computer chips.

The achievement, published in the September issue of the journal Nature Nanotechnology, offers a promising and powerful new tool for use in a wide range of fields and industries such as biomedicine, electronics and IT that seek ways to exploit the often unique properties of so-called nanoparticles, i.e. particles that are smaller than 100 nanometers.

Until now, standard top-down microfabrication techniques produce such tiny particles by in effect carving them out of a bigger piece of material. Printing, in contrast, adds ready-made nanoparticles onto a surface in a very efficient way and thus facilitates the combination of different materials such as metals, polymers, semiconductors, and oxides.

For the first time, IBM researchers have printed particles as tiny as 60 nanometers—roughly 100 times smaller than a human red blood cell—with single-particle resolution to create nanopatterns ranging from simple lines to complex arrangements. Translating their resolution into "dots per inch" (dpi), a standard measure that defines how many individual spots of ink can be printed on a certain area, the nanoprinting method yields 100,000 dots per inch, whereas common offset printing today operates with 1,500 dpi.

To demonstrate the efficiency and the versatility of their method, IBM researchers chose to print Robert Fludd's famous 17th-century drawing of the sun, which was alchemists' symbol for gold. Quite fittingly, it is printed out of roughly 20,000 gold particles, each of them 60 nanometers in diameter. The printing method precisely placed one particle per dot, thus creating the smallest piece of artwork ever printed from single pigment particles.
Nanoprinting applications

"This method opens up new ways to precisely and efficiently position various kinds of nanoparticles on different surfaces, a prerequisite for exploiting the unique properties of such nanoparticles and for making their use economically feasible," explains Heiko Wolf, researcher in nanopatterning at IBM's Zurich Research Lab.

In biomedicine this printing process could, for example, be applied to the printing of large arrays of biofunctional beads that can detect and identify certain cells or markers in the body. One example could be rapid screening for cancer cells or heart attack markers. As part of new point-of-care diagnostic devices, regular arrays of functional beads could enable a fast and automated read-out that only needs the tiniest amounts of samples.

Nanoparticles can also interact with light. With the new method, optical materials with new properties could be printed, for example, for use in optoelectronic devices. So-called "metamaterials" could be created in which the printed structures are as small as the wavelength of the light and therefore act as if they were a single lens with unusual properties.